Nano-Biocomposite Materials Obtained from Laser Ablation of Hemp Stalks for Medical Applications and Potential Component in New Solar Cells

The study in this paper presents a new material that was produced as a thin film by the Pulsed Laser Deposition technique (PLD) using a 532 nm wavelength and 150 mJ/pulse laser beam on the hemp stalk as target. The analyses performed by spectroscopic techniques (Fourier Transform Infrared Spectroscopy—FTIR, Laser—Induced Fluorescence Spectroscopy—LIF, Scanning Electron Microscopy coupled with Energy Dispersive X-ray—SEM-EDX, Atomic Force Microscopy—AFM and optical microscope) evidenced that a biocomposite consisting of lignin, cellulose, hemicellulose, waxes, sugars and phenolyc acids p-coumaric and ferulic, similar to the hemp stalk target was obtained. Nanostructures and aggregated nanostructures of 100 nm to 1.5 μm size were evidenced. Good mechanical strength and its adherence to the substrate were also noticed. It was noticed that the content in calcium and magnesium increased compared to that of the target from 1.5% to 2.2% and from 0.2% to 1.2%, respectively. The COMSOL numerical simulation provided information on the thermal conditions that explain phenomena and processes during laser ablation such as C-C pyrolisis and enhanced deposition of calcium in the lignin polymer matrix. The good gas and water sorption properties due to the free OH groups and to the microporous structure of the new biocomposite components recommends it for studies for functional applications in medicine for drug delivery devices, filters in dialysis and for gas and liquid sensors. Functional applications in solar cells windows are also possible due to the conjugated structures of the contained polymers.


Introduction
The complex composite structure of hemp stalk makes it of interest for studies in order to develop new technologies of fabrication designed to enlarge the number of products that can be manufactured from Cannabis Sativa. Hemp is a plant of great industrial potential and has been used at least since five thousand years ago, with archaeological discoveries being recently reported [1]. The structure and components of hemp stalk have been

Micrography and Elemental Composition
After deposition, the HMP-STK target and the thin film deposited on glass slab were analyzed with electron microscopy (SEM) and the images are presented in Figure 1a,b. It can be observed that a continuous thin film was obtained consisting of droplets or agglomerations. Agglomerations can be also observed in the SEM images of the HMP-STLK (Figure 1a,c,e) and on the surface of the PLD-HMP-STK/HMP-FB sample (Figure 1f). The red-brownish color of the material of the PLD-HMP-STK thin films is observed in the optical microscopic images in Figure 2c,d. In Figure 1c, the transparency of the PLD-HMP-STK/Glass thin film can be noticed, as well as opaque, whitish formations that look like splashes. Their appearance corresponds to similar formations in the hemp stalk in the optical microscopic images of Figure 2a,b. The SEM images obtained two years after deposition of the thin films exhibit cracks in the PLD-HMP-STK/Glass due to multiple manipulations and the scratching procedure for FTIR analysis. However, we consider that the thin layer has a good mechanical strength and adhesion to the glass substrate. The elemental composition of the PLD-HMP-STK on glass and on HMP-FB is similar to the target elemental composition and presents inhomogeneities for different areas when analyzed by EDX. An increase in calcium and magnesium concentration can be observed from an average of 1.5% calcium and 0.2% magnesium in the HMP-STK target to an average of 2.2% calcium and 1.2% magnesium in the PLD-HMP-STK thin films, while carbon content decreased from an average of 66% in HMP-STK target to 50% or less in the PLD-HMP-STK thin films. Due to the inhomogeneous disposition of the constituents, a conclusion cannot be drawn in this regard. 2.2% calcium and 1.2% magnesium in the PLD-HMP-STK thin films, while carbon content decreased from an average of 66% in HMP-STK target to 50% or less in the PLD-HMP-STK thin films. Due to the inhomogeneous disposition of the constituents, a conclusion cannot be drawn in this regard.

AFM: Atomic Force Microscopy Nanosurf Easy Scan 2, Liestal, Switzerland
The rough structure of the thin layer deposited on the glass (PLD-HMP-STK/Glass) of an unevenly distributed topography can be seen in Figure 3. Craters of 151 nm and 290 nm are noticed in the 1D topography plots on thin film thickness in Figure 3b,e. Aggregated structures and droplets of different sizes from 100 nm to 1.5 μm or even 6 μm are  The rough structure of the thin layer deposited on the glass (PLD-HMP-STK/Glass) of an unevenly distributed topography can be seen in Figure 3. Craters of 151 nm and 290 nm are noticed in the 1D topography plots on thin film thickness in Figure 3b,e. Aggregated structures and droplets of different sizes from 100 nm to 1.5 µm or even 6 µm are noticed in the 2D images of topography (Figure 3a,d,g,j). In Figure 3, the 1D plots (e) and (h) of the thin film topography show two structures assigned to droplets. The measurements of size droplets were performed on the x-axis as FWHM (full width at half maximum) and on the z-axis. The droplets' widths were 4.78 µm and 2.610 µm, respectively, while the droplets' heights were 357 nm and 98 nm. The topographic lines (Figure 3b,e,h,k) also indicate overlapping or clumped droplets by the jagged appearance of the lines [21], this indicates that most of the micrometric structures are in fact the result of nanostructure aggregation. The roughness is well observed in the 3D plots (Figure 3c,f,i,l). The AFM images were acquired after various manipulation including collecting material from the PLD-HMP-STK thin film for the FTIR analysis. Therefore, the "channels" of 623 nm to 1.42 µm depth observed in the plots of Figure 3g-l are due to cracking or they resulted during scratching for the sample collecting purpose.

AFM: Atomic Force Microscopy Nanosurf Easy Scan 2, Liestal, Switzerland
The rough structure of the thin layer deposited on the glass (PLD-HMP-STK/Glass) of an unevenly distributed topography can be seen in Figure 3. Craters of 151 nm and 290 nm are noticed in the 1D topography plots on thin film thickness in Figure 3b,e. Aggregated structures and droplets of different sizes from 100 nm to 1.5 μm or even 6 μm are noticed in the 2D images of topography (Figure 3a,d,g,j). In Figure 3, the 1D plots (e) and (h) of the thin film topography show two structures assigned to droplets. The measurements of size droplets were performed on the x-axis as FWHM (full width at half maximum) and on the z-axis. The droplets' widths were 4.78 μm and 2.610 μm, respectively, while the droplets' heights were 357 nm and 98 nm. The topographic lines ( Figure  3b,e,h,k) also indicate overlapping or clumped droplets by the jagged appearance of the lines [21], this indicates that most of the micrometric structures are in fact the result of nanostructure aggregation. The roughness is well observed in the 3D plots (Figure 3c,f,i,l). The AFM images were acquired after various manipulation including collecting material from the PLD-HMP-STK thin film for the FTIR analysis. Therefore, the "channels" of 623 nm to 1.42 μm depth observed in the plots of Figure 3g-l are due to cracking or they resulted during scratching for the sample collecting purpose.

Functional Groups Analysis in FTIR Spectroscopy
The FTIR spectra of the target HMP-STK and the thin film PLD-HMP-STK ( Figure 4) are very similar, denoting that the functional groups are well preserved during laser ablation. The vibrational modes and corresponding functional groups are presented in Table  1

Functional Groups Analysis in FTIR Spectroscopy
The FTIR spectra of the target HMP-STK and the thin film PLD-HMP-STK ( Figure 4) are very similar, denoting that the functional groups are well preserved during laser ablation. The vibrational modes and corresponding functional groups are presented in Table 1  Hemp fabric (HMP-FB) made of yarns produced from hemp fiber from stalks was used to compare and to evidence the good preservation of the he stituents in the PLD-HMP-STK. The HMP-FB spectrum was used to compa obtained by laser ablation and deposition. During the technological process fabrication, the stalk was water-retted and the hurds (the wood in the HM   C-H bending [24]; methoxyphenolic substitution in the aromatic ring [8,24]; H in-plane bending in phenols in lignin [24] O-H in-plane bending, intermolecular bonded in alcohols in polymers [5,24]  Skeletal vibrations due to C-O-C asymmetric st in the oxane ring (cyclic ethers) [24] Side groups vibrations [4,24] C=C bending in alkene in the carboxylic acids [24] cellulose Hemicellulose Starch Pectin p-coumaric and ferulic acids 880 880 -Skeletal vibrations due to C-O-C symmetric st, C-C-O and C-C-H bendings [4,5,21,24]; C=C bending in alkene in the carboxylic acids [24] cellulose Hemicellulose Starch Pectin p-coumaric and ferulic acids -827 -C=C bending in alkene trisubstituted [24] p-coumaric and ferulic acids  [24]; C=C bending in alkene disubstituted (cis) in the carboxylic acids [24] O-H out-of-plane bending [24] C-H bending [24] Cellulose p-coumaric and ferulic acids 675 696 -C-H bending and ring bending [24]; C=C bending in alkene disubstituted (cis) in the carboxylic acids [24] C-H aromatic bending-out-of-plane modes [26] Adsorbed molecular CO 2 [26] O-H out-of-plane bending [24]; C-OH out-of-plane bending [5,24] cellulose crystalline state, hemicellulose, starch, sugars, lignin p-coumaric and ferulic acids adsorbed CO 2 650-624 650-624 650-624 O-H out-of-plane bending [24] C-OH out-of-plane bending [5,24] cellulose, hemicellulose, starch, sugars, lignin p-coumaric and ferulic acids adsorbed water Hemp fabric (HMP-FB) made of yarns produced from hemp fiber from water-retted stalks was used to compare and to evidence the good preservation of the hemp stalk constituents in the PLD-HMP-STK. The HMP-FB spectrum was used to compare the results obtained by laser ablation and deposition. During the technological process for HMP-FB fabrication, the stalk was water-retted and the hurds (the wood in the HMP-STK) were mostly removed during the primary processing in the retting mills. After that, during preparation for spinning and weaving, the fiber lost more of the remaining wood and other components were removed through physical and chemical processes of combing, boiling, alkali treatments and bleaching with oxygen peroxide. The 2971 cm −1 peaks assigned by Malgorzata Zimniewska et al., 2018 [7] to aryl C-H in lignin combined with the 1510 cm −1 band of C=C aromatic symmetrical stretching vibrations [5,7,24] and the methoxyphenolic substitution in the aromatic ring denoted by the 1359 cm −1 peak also assigned to O-H bending in phenols and in alcohols [5,24], as well as the O-H vibrations in phenol polymers at 3480 cm −1 , indicate that lignin is still present in the HMP-FB material. Additionally, a number of low intensity peaks in the 4000-3800 cm −1 range are noticed which can be assigned to free O-H stretching. The low intensity bands in the 650-700 cm −1 range can be assigned to C-H aromatic bending-out-of-plane modes. In the case of HMP-FB, the lignin noticed in the FTIR spectrum is contained in the fibers while the lignin evidenced in the PLD-HMP-STK is sourced in all of the hemp stalks' structural constituents (wood, fibers etc.). Most of the phenolic peaks of the PLD-HMP-STK spectrum are identical to the HMP-STK spectrum, and only a slight shift in the C-H aromatic bending-out-of-plane mode is noticed from 675 cm −1 to 696 cm −1 .
Cellulose is evidenced in all three spectra of HMP-STK, PLD-HMP-STK and HMP-FB by the peaks at 3362/3382/3328 cm −1 of O-H intermolecularly bonded in alcohol in polymers. The spectra of HMP-STK and PLD-HMP-STK also exhibit vibrations specific to free O-H in alcohols at 3848 cm −1 , which are of very low intensity, with most missing in the HMP- are also evidenced in the HMP-STK and PLD-HMP-STK spectra denoted by the peaks at 3938 cm −1 , 3848 cm −1 , and mainly by the peak at 1639 cm −1 for water and the peak at 2462 cm −1 . These peaks are missing in the HMP-FB spectrum. These adsorbing properties are due to an effective microporous structure that can be noticed in the AFM images of the thin film of PLD-HMP-STK topography ( Figure 3). Additionally, the free O-H phenolic and alcoholic groups in lignin and cellulose, respectively, indicated by the vibrations at 3938 cm −1 and 3848 cm −1 , are available to H-bonding with the C=O groups in CO 2 and in formaldehyde and with the O-H groups in water, as schematically represented in Figure 5.
The adsorbed formaldehyde exhibited by the vibrations at 1554 cm −1 and 1747 cm −1 in HMP-STK and PLD-HMP-STK and which are missing in HMP-FB denote good adsorbing properties of the PLD-HMP-STK material. Adsorbed water and adsorbed carbon dioxide are also evidenced in the HMP-STK and PLD-HMP-STK spectra denoted by the peaks at 3938 cm −1 , 3848 cm −1 , and mainly by the peak at 1639 cm −1 for water and the peak at 2462 cm −1 . These peaks are missing in the HMP-FB spectrum. These adsorbing properties are due to an effective microporous structure that can be noticed in the AFM images of the thin film of PLD-HMP-STK topography ( Figure 3) [30] published a study on cellulose acetate-based membranes for the removal of uremic toxins from dialysate. The adsorbing property of the polymeric thin film PLD-HMP-STK makes it a candidate to be used as a matrix in drug delivery devices, including transdermal patches. The components of PLD-HMP-STK thin film consisting of lignin, cellulose and, most importantly, phenolic carboxylic acids p-coumarin and ferulic, due to their antioxidant properties, are also recommended as an active material for transdermal patches for cosmetics and dermatology. The gas-adsorbing property of PLD-HMP-STK makes it a candidate material for gas sensing in medicine and for applications in other fields where gas sensing is required. Additionally, PLD-based techniques can be applied in 3D printing and the ablated material from HMP-STK can be used  [30] published a study on cellulose acetate-based membranes for the removal of uremic toxins from dialysate. The adsorbing property of the polymeric thin film PLD-HMP-STK makes it a candidate to be used as a matrix in drug delivery devices, including transdermal patches. The components of PLD-HMP-STK thin film consisting of lignin, cellulose and, most importantly, phenolic carboxylic acids p-coumarin and ferulic, due to their antioxidant properties, are also recommended as an active material for transdermal patches for cosmetics and dermatology. The gas-adsorbing property of PLD-HMP-STK makes it a candidate material for gas sensing in medicine and for applications in other fields where gas sensing is required. Additionally, PLD-based techniques can be applied in 3D printing and the ablated material from HMP-STK can be used as a filler or to develop components for drug delivery devices. The PLD-HMP-STK thin film is also a candidate for solar cell windows.

Numerical Simulation in COMSOL 5.6
The diagrams in Figure 6 are 2D plots resulting from the simulation in COMSOL and show the temperature evolution during laser irradiation over time. The influences of heat diffusion between the composite lignin/Ca components are observed in Figure 6d-f where the maximum temperatures are shifted from the center of the spot (the center of the spot is at 25.4 mm in the diagrams) and where the maximum heating is obtained, which is usually when simulating the laser heating of homogeneous materials [21,[31][32][33].
The diagrams in Figure 6 are 2D plots resulting from the simulation in COMSOL and show the temperature evolution during laser irradiation over time. The influences of heat diffusion between the composite lignin/Ca components are observed in Figure 6d-f where the maximum temperatures are shifted from the center of the spot (the center of the spot is at 25.4 mm in the diagrams) and where the maximum heating is obtained, which is usually when simulating the laser heating of homogeneous materials [21,[31][32][33]. In order to evaluate the results of the simulation, the maximum temperatures in the individual targets of Ca and lignin and of each calcium and lignin component in the lignin/Ca composite as well as the temperatures of equilibrium were centralized in Table 2 based on the times when they were achieved. The data in Table 2 were plotted as shown in Figure 7. Compiling the optical and thermal parameters of the materials, the simulation shows enhancements of thermal effects in the lignin/Ca composite for both components (Tmax-Ca in lignin/Ca and Tmax-lignin in lignin/Ca) compared to the values achieved on the individual targets (Tmax-Ca and Tmax-lignin). Lignin better absorbs laser irradiation than calcium and laser heating is more effective on the component (Tmax-lignin in lignin/Ca) in the composite target. The maximum temperature of the component (Tmax-Ca in lignin/Ca) is considered the equilibrium temperature (Teq lignin/Ca in spot) achieved in the center of the spot due to laser heating and the thermal diffusion effect.  In order to evaluate the results of the simulation, the maximum temperatures in the individual targets of Ca and lignin and of each calcium and lignin component in the lignin/Ca composite as well as the temperatures of equilibrium were centralized in Table 2 based on the times when they were achieved. The data in Table 2 were plotted as shown in Figure 7. Compiling the optical and thermal parameters of the materials, the simulation shows enhancements of thermal effects in the lignin/Ca composite for both components (Tmax-Ca in lignin/Ca and Tmax-lignin in lignin/Ca) compared to the values achieved on the individual targets (Tmax-Ca and Tmax-lignin). Lignin better absorbs laser irradiation than calcium and laser heating is more effective on the component (Tmaxlignin in lignin/Ca) in the composite target. The maximum temperature of the component (Tmax-Ca in lignin/Ca) is considered the equilibrium temperature (Teq lignin/Ca in spot) achieved in the center of the spot due to laser heating and the thermal diffusion effect. 1792 K 1645 K Tmax-Ca in pure Ca target in spot center (x,y,z) = (0,0,0) 804 K 930 K 904 K Tmax-lignin in pure lignin target in spot center (x,y,z) = (0,0,0) 1444 K 1742 K 1635 K The temperatures reached on the lignin component indicate conditions that can to processes similar to pyrolysis. Depolymerization of lignin is therefore expected in sense that Kawamoto, H. et al., 2017 [34] describes lignin pyrolysis, thus meaning th C and C-O bonds attached to the aromatic ring may break. Under laser ablation condi recombinations of chemical structures resulting from the pyrolysis-like phenomena place in the plasma of ablation. These recombinations are confirmed by the FTIR spe However, the temperatures achieved during laser ablation last only a few nanosec and could also contribute to the good preservation of the basic structure of lignin; li is only partially depolymerized, meaning that the result consists of a shorter poly chain and does not lead to monomers.
The basic structures are not affected and comparing the FTIR spectra and SEM crography of HMP-STK and PLD-HMP-STK (Figures 1 and 4), as well as the AFM yses performed on PLD-HMP-STK (Figure 3), there are indications that the materia posited in the PLD process consists of micrometric and submicrometric structures o initial constituents of the hemp stalk biocomposite HMP-STK.
The simulation also provides information on the heating enhancement processe both lignin and calcium; this could explain the increase in calcium content in the P HMP-STK compared to the HMP-STK target.

LIF Spectroscopy Analysis
For LIF spectroscopy performed on the thin films PLD-HMP-STK/Glass and P HMP-STK/HMP-FB, an excitation laser beam of 355 nm was used, and the installati presented in Figure 8. The characteristic fluorescence peak of the thin film PLD-H The temperatures reached on the lignin component indicate conditions that can lead to processes similar to pyrolysis. Depolymerization of lignin is therefore expected in the sense that Kawamoto, H. et al., 2017 [34] describes lignin pyrolysis, thus meaning that C-C and C-O bonds attached to the aromatic ring may break. Under laser ablation conditions, recombinations of chemical structures resulting from the pyrolysis-like phenomena take place in the plasma of ablation. These recombinations are confirmed by the FTIR spectra. However, the temperatures achieved during laser ablation last only a few nanoseconds and could also contribute to the good preservation of the basic structure of lignin; lignin is only partially depolymerized, meaning that the result consists of a shorter polymer chain and does not lead to monomers.
The basic structures are not affected and comparing the FTIR spectra and SEM micrography of HMP-STK and PLD-HMP-STK (Figures 1 and 4), as well as the AFM analyses performed on PLD-HMP-STK (Figure 3), there are indications that the material deposited in the PLD process consists of micrometric and submicrometric structures of the initial constituents of the hemp stalk biocomposite HMP-STK.
The simulation also provides information on the heating enhancement processes on both lignin and calcium; this could explain the increase in calcium content in the PLD-HMP-STK compared to the HMP-STK target.

LIF Spectroscopy Analysis
For LIF spectroscopy performed on the thin films PLD-HMP-STK/Glass and PLD-HMP-STK/HMP-FB, an excitation laser beam of 355 nm was used, and the installation is presented in Figure 8. The characteristic fluorescence peak of the thin film PLD-HMP-STK/HMP-FB is noticed at 508 nm, as well as a number of secondary peaks due to chemical reactions [21,27,29] and to laser interactions with different constituents of the thin film, such as p-coumaric acid emitting at 430 nm and 455 nm [35,36] and ferulic acid with emissions noticed at 480 nm and 498 nm [37,38], as seen in the spectrum of Figure 9 and Table 3. In the LIF spectrum of PLD-HMP-STK/Glass (Figure 9 and Table 3), peaks of coumaric and ferulic acids are noticed at 424 nm, 443 nm, 452 nm, 482 nm and 498 nm, respectively, while peaks at 603 nm and 627 nm are assigned to chlorophyll [35,37,38]. Peaks at 549 nm, 561 nm, 587 nm, 603 nm, 614 nm, 640 nm and 668 nm denoting secondary reactions during 355 nm laser beam interactions with the PLD-HMP-STK/Glass thin film are also observed in the spectrum of Figure 9. The enhanced fluorescence intensity of PLD-HMP-STK/Glass compared to PLD-HMP-STK/HMP-FB can be explained due to the continuous phase of the former, while the latter thin film is more of a dispersion of nano-and microparticles within the fibers of the HMP-FB. The two tower bands in the ranges of 482-508 nm and 587-627 nm are assigned to a radical formation [29] and to depolymerization processes under laser irradiation. such as p-coumaric acid emitting at 430 nm and 455 nm [35,36] and ferulic acid with emissions noticed at 480 nm and 498 nm [37,38], as seen in the spectrum of Figure 9 and Table  3. In the LIF spectrum of PLD-HMP-STK/Glass ( Figure 9 and Table 3), peaks of coumaric and ferulic acids are noticed at 424 nm, 443 nm, 452 nm, 482 nm and 498 nm, respectively, while peaks at 603 nm and 627 nm are assigned to chlorophyll [35,37,38]. Peaks at 549 nm, 561 nm, 587 nm, 603 nm, 614 nm, 640 nm and 668 nm denoting secondary reactions during 355 nm laser beam interactions with the PLD-HMP-STK/Glass thin film are also observed in the spectrum of Figure 9. The enhanced fluorescence intensity of PLD-HMP-STK/Glass compared to PLD-HMP-STK/HMP-FB can be explained due to the continuous phase of the former, while the latter thin film is more of a dispersion of nano-and microparticles within the fibers of the HMP-FB. The two tower bands in the ranges of 482-508 nm and 587-627 nm are assigned to a radical formation [29] and to depolymerization processes under laser irradiation. Bathochromic and hypsochromic shifts are also noticed for similar peaks in the two spectra of Figure 9 and can be explained as an influence of the different deposition substrates, including their morphology, which affects the morphology of the film and its consistency.    Violet-blue due to pcoumaric acid and its derivatives [37,38]; bathochromic shift on PLD-HMP-STK/Glass -443 Blue due to coumaric acid derivatives [37,38] 455 452 Blue due to coumaric acid [37,38]; bathochromic shift on PLD-HMP-STK/Glass 480 482 v. strong Blue-green due to ferulic acid [35,36]; slight hypsochromic shift 498 489 v. strong Blue-green due to ferulic acid [35,36]; bathochromic shift and enhanced intensity due to the p-coumaric acid concentration [35] on PLD-HMP-STK/Glass Bathochromic and hypsochromic shifts are also noticed for similar peaks in the two spectra of Figure 9 and can be explained as an influence of the different deposition substrates, including their morphology, which affects the morphology of the film and its consistency.

Materials
The hemp stalk noted as HMP-STK (Figure 2a

Method of Work
After drying naturally at room temperature (20-25 • C) for one year, the hemp stalk was subject to different tests under laser irradiation. Two tests are presented in this paper, both using a YG 981E/IR-10 laser system: Quantel-YG980 Q-switched Nd:YAG laser, Quantel, Les Ulis, France. The installation is presented in Figure 8.
The test was designed to obtain thin films by pulsed laser deposition (PLD), which involves controlled atmosphere laser ablation. Small bundles, as shown in Figure 10, were made from crushed stalk (simulating "decortication process"). The bundles resulted from the crushed hemp stalk (HMP-STK) were irradiated and the effects were studied while the method was improved until thin films were deposited on the glass slab (PLD-HMP-STK/Glass- Figure 2b) and on the hemp fabric (PLD-HMP-STK/HMP-FB- Figure 2c).
Quantel, Les Ulis, France. The installation is presented in Figure 8.
The test was designed to obtain thin films by pulsed laser deposition (PLD), which involves controlled atmosphere laser ablation. Small bundles, as shown in Figure 10, were made from crushed stalk (simulating "decortication process"). The bundles resulted from the crushed hemp stalk (HMP-STK) were irradiated and the effects were studied while the method was improved until thin films were deposited on the glass slab (PLD-HMP-STK/Glass- Figure 2b) and on the hemp fabric (PLD-HMP-STK/HMP-FB- Figure 2c). The thin film deposition was conducted in the vacuum chamber of the laser installation. The 532 nm laser beam of 300 μm radius was used with a pulse width of 10 ns, 10 Hz repetition rate and 150 mJ/pulse. The pressure in the deposition chamber was of 10 −2 Torr, the distance between the target to the support for thin film deposition was of 30 mm, and the deposition was 30 min long. The parameters and conditions for the PLD process were chosen in order to preserve most of the polymer chemical structure [21,27,29]. Additionally, the numerical simulation completed the information regarding plasma threshold conditions and for adjustments regarding the PLD procedure. The thin film deposition was conducted in the vacuum chamber of the laser installation. The 532 nm laser beam of 300 µm radius was used with a pulse width of 10 ns, 10 Hz repetition rate and 150 mJ/pulse. The pressure in the deposition chamber was of 10 −2 Torr, the distance between the target to the support for thin film deposition was of 30 mm, and the deposition was 30 min long. The parameters and conditions for the PLD process were chosen in order to preserve most of the polymer chemical structure [21,27,29]. Additionally, the numerical simulation completed the information regarding plasma threshold conditions and for adjustments regarding the PLD procedure.

Fourier Transform Infrared Spectroscopy Analysis
The chemical composition was analyzed with Fourier Transform Infrared Spectroscopy Bomem MB154S spectrometer at an instrumental resolution of 4 cm −1 (Bomem, ABB group, Québec, QC, Canada). To prepare the pill for FTIR analysis, pieces of approximately 0.5 cm long were cut from the material used as a target; it was finally cut, then it was ground and mixed with potassium bromide in a mortar, then pressed into a pellet. For the thin layer (PLD-HMP-STK) analysis, the material was scraped from the surface of the film deposited on the glass slab and then mixed in a mortar together with KBr, after which the pellet was obtained with the hydraulic press [21,27,29].

Scanning Electron Microscopy Coupled with Energy Dispersive X-ray Analysis
SEM-EDS was used to analyze the morphology and elemental composition: the Scanning Electron Microscope coupled with Energy Dispersive X-Ray (SEM-EDS) investigation with Vega Tescan LMH II, Brno, Cehia.

Atomic Force Microscopy Analysis
The topography of PLD-HMP-STK/Glass was analyzed using AFM: Atomic Force Microscopy Nanosurf Easy Scan 2, Liestal, Switzerland.

Conclusions
The studies carried out for this paper led to obtaining a new material using the PLD technique. The new material consists of a thin film of nanostructures and aggregated nanostructures with chemical composition and composite constituents similar to that of the hemp stalk that was used as a target. These results, highlighted by spectral analysis, implicitly denote a good level of preservation of the functional groups and of the constituents of the hemp stalk biocomposite; this is better than in the case of the fabric obtained from hemp fibers manufactured by classical methods. The thin films show good mechanical strength and adhesion to the glass substrate.
The spectra of the thin films also show good water and gas sorption properties, which therefore recommend them as candidate materials for medical applications such as a matrix constituent in transdermal patches and in gas sensors. In addition, this type of thin film could be used for solar cell windows applications due to their components of conjugated chemical structures.
The numerical simulation in COMSOL, providing information on temperatures achieved during ablation and temperature dynamics in time and space, contributed to a better and more extensive evaluation of the phenomena and processes that occurred during ablation and proved to be an important tool for performing and interpreting the experimental results.